Instead of running off, again, on a wild goose chase, it maybe would be simpler to just read keys, the official documentation? It mentions there that:

Starting with Perl 5.14, keys can take a scalar EXPR, which must contain a reference to an unblessed hash or array. The argument will be dereferenced automatically. This aspect of keys is considered highly experimental. The exact behaviour may change in a future version of Perl.

... and without seeing your code, my guess is that you are "using" that experimental feature, knowingly or not.

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Re^3: How do you find keys of a Blessed Hash?
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keys $blessed doesn't work for a very good reason. keys can (in recent versions of Perl) be used with either arrays or hashes. A blessed object can (thanks to overload) be simultaneously dereferencable as a hash and and array. So for blessed objects, you need to manually dereference.

Sure, those work fine, but aren't really new work, just syntactic sugar over $x = defined($x) ? $x : $value, a local $\ = "\n" (and print), and a function closed over a variable declared in an outer lexical scope (this is actually superior to the sugar, since you can have multiple functions sharing the same variable).